Data storage devices using various kinds of media, such as optical disks and magnetic tapes, have been known in the art. In particular, hard disk drives (HDDs) have been widely used as storage devices for computers and have been one of the indispensable devices used in current computer systems. Moreover, the HDDs have found widespread application in motion picture recording/reproducing apparatuses, car navigation systems, cellular phones, mobile media players, digital video recorders, etc., in addition to computers, because of their outstanding performance characteristics.
Magnetic disks used in current HDDs have multiple concentric data tracks and servo tracks provided discretely in the disk circumferential direction. User data are recorded in units of data sectors and a data sector is recorded between servo sectors. A swing actuator moves a head slider above a spinning magnetic disk. A head element portion of a head slider accesses a desired data sector in accordance with position information indicated by servo data to write data to the data sector or to read data from the data sector.
The head element portion is fixed to a slider to constitute a head slider. The head slider is secured to a swing actuator. The slider flies above a spinning magnetic disk and the actuator positions the head slider (head element portion) to a desired radial position on the magnetic disk. In reading data, the signal read from the magnetic disk by the head element portion undergoes predetermined signal processing such as waveform shaping and decoding with a signal processing circuit and then is transmitted to a host. The transfer data from the host undergo predetermined processes by the signal processing circuit and then are written to the magnetic disk.
In a HDD, airflow generated by the spin of a magnetic disk creates numerous problems. For example, the airflow may cause the actuator to sway, which disturbs accurate positioning of the head. In addition, vibrations of the magnetic disk (disk flutter) caused by the turbulence of the airflow generated by the magnetic disk's spin causes writing and reading errors. The disk flutter disturbs accurate positioning of the head to a track as well as the head's sway. Such vibrations caused by airflow are called flow induced vibration (Fly).
For HDDs, suppression of the FIV has been consistently used to increase head positioning accuracy. In particular, as recording density in a magnetic disk increases to attain higher tracks per inch (TPI) in order to store more information on a smaller area, more accurate head positioning is required. Therefore, even small disk flutters are becoming problematic in advanced HDDs having higher TPI's.
To improve the FIV characteristic in a HDD, a disk damper plate, which is a plate facing a disk mounted in the HDD, has been considered as a way to lessen FIV. For example, Japanese Unexamined Patent Application Pub. No. 2008-152891 proposes a HDD in which an airflow guide plate (according to the term used in the reference) is provided upstream of the actuator. The airflow guide plate is mounted by being inserted in a groove in a shroud formed on a sidewall section of the base.
A disk damper plate weakens airflow above a magnetic disk toward the actuator in order to reduce turbulence vibrations of a magnetic head. In addition, the disk damper plate weakens the airflow above the magnetic disk to suppress disk flutter. The effect of a disk damper plate to suppress disk flutter depends on the reduction in the amount and the speed of the airflow.
Spin of a magnetic disk generates airflow above the main plane (the plane vertical to the rotational axis) of the disk. If a disk damper plate is inserted between magnetic disks or between a magnetic disk and the top cover, the volume of the space decreases, so the amount of flow decreases. With respect to the cross-section in a direction of the rotational axis, the disk damper plate blocks the airflow, so the speed of the airflow decreases.
In this way, the disk flutter suppression effect of the disk damper plate is attained by restricting the airflow parallel to the main plane of the magnetic disk. However, the airflow caused by the spin of the magnetic disk is not only the airflow parallel to the main plane of the magnetic disk. There exists airflow caused by disk spin in the direction vertical to the main plane of the magnetic disk, too. There is a gap between the magnetic disk and the inside sidewall of the base. The air flows upward or downward in the gap.
Disk flutter includes vibrations of a magnetic disk parallel to the rotational axis, and is caused by the air flowing between the outer edge of the magnetic disk and the inside sidewall of the base. Accordingly, it is desirable to restrict the airflow vertical to the main plane of the magnetic disk in addition to the airflow parallel to the main plane of the magnetic disk.
In the HDD disclosed in Japanese Unexamined Patent Application Pub. No. 2008-152891, the airflow guide plate is inserted in a groove of a shroud formed on the sidewall of the base. Thus, the path between the magnetic disk and its base mount is blocked by the airflow guide plate, so an effect is expected that restricts airflow upward or downward on the outer edge of the magnetic disk.
However, shaping a shroud groove on the inside sidewall of the base requires time and effort, which is not preferable for the manufacturing efficiency and costs of HDDs. Further, a manufacturing step of inserting the airflow guide plate into the shroud groove is required, which degrades the manufacturing efficiency of the HDDs. In addition, as indicated in Japanese Unexamined Patent Application Pub. No. 2008-152891, friction in inserting the airflow guide plate into the shroud groove may produce dusts and/or debris. Accordingly, a technique that restricts air flowing upward or downward between the outer edge of the magnetic disk and the inside sidewall of the base, which also alleviates the inefficiencies associated with current techniques, is desirable.